User operated controllers for air conditioning systems, commonly known as thermostats, should provide lighting for the visual display of control features, including actual temperature, temperature setpoints and operating mode, as well as lighting for the keypad switches which are user operated to set the control functions of the thermostat and to observe system operating conditions. However, thermostats with continuously lit visual displays and control switches are inefficient since they continuously consume energy when not required to do so, and the operating lives of the devices providing illumination, such as electroluminescent lamps and light emitting diodes are shortened. Accordingly, there has been a need to improve the lighting features of air-conditioning system thermostats whereby a thermostat visual display is lighted only when needed and certain user actuated switches or so-called key or pushbutton switches are illuminated also only when needed. In this way, energy savings may be obtained, certain elements may be eliminated from the thermostat, such as ambient light sensors, and the risk of unacceptable lighting element degradation or failure is reduced, all so as to reduce the cost of the thermostat and its operation.
There has also been a need recognized for providing a thermostat with a user actuated switch whereby the automatic preset energy saving temperature setback feature may be implemented to immediately change the temperature setpoints to the setback setpoints without a lengthy user controlled data entry process. In other words, there has been a need to provide a thermostat which, upon actuation of a single switch, will cause the temperature setpoints to adjust immediately to previously installed setback or offset temperature setpoints.
It is to provide for the above-mentioned needs and desiderata in the art of air conditioning system thermostats that the present invention has been developed.